Method and device for joint replacement

ABSTRACT

A prosthesis including a hemiarthroplasty cup including an inner surface shaped and sized to accommodate a reamed or unreamed femoral head outer surface, and an outer surface shaped and sized to accommodate a reamed or unreamed acetabulum outer surface of an acetabulum socket, wherein the hemiarthroplasty cup is configured to maintain allowance of articulation of the femoral head outer surface and the acetabulum socket relative to the hemiarthroplasty cup after implantation.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of, and incorporates by reference,U.S. Provisional Patent Application No. 61/676,041 filed on Jul. 26,2012 entitled “Method and Device for Joint Replacement.”

RELATED FIELD

The method and device for joint replacement relates to joint repair andreplacement.

BACKGROUND

Joints provide articulation of various body parts. These joints can bedamaged in numerous ways, such as exposure to trauma or degeneration dueto old age or disease. Joints, such as hip joints, typically include abone with a ball end and a bone with a socket opening. When damaged, theinteraction between the ball and socket can become problematic,preventing proper articulation of a joint and/or pain in the joint. Suchrestriction and/or discomfort are often due to a breakdown of thesurfaces of one or both of the ball and socket. In the case of a hipjoint, the femur and pelvis are involved. The femur includes the femoralhead with a layer of articular cartilage and the pelvic bone includesthe acetabulum socket, also with a layer of articular cartilage. Oncethe layer of articular cartilage is worn or damaged to an advanceddegree, the joint no longer functions as intended and can requiresurgical intervention.

Currently, to address worn or damaged hip joints, an invasive surgicalprocedure is performed to install a full or half prosthetic joint. Theinstallation of the prosthetic joint involves substantial restructuringof the original joint, which requires the surgeon to inflict substantialdamage to the joint area to access and install the prosthetic joint,thereby increasing the likelihood of permanent damage to surroundingnerves, ligaments, etc. In addition, this invasive procedure can resultin chronic pain, poor articulation of the joint, failure of theprosthesis, etc., which can substantially decrease the likelihood of apost-operative normally functioning prosthetic joint.

Accordingly, it would be desirable to provide a minimally invasiveprocedure that limits the damage to the joint area during installationand provide a more reliable prosthetic repair/replacement.

BRIEF SUMMARY

In at least some embodiments, the method of joint replacement relates toforming one or more arthroscopy portals adjacent a hip joint thatincludes a femur and a pelvis; inserting a guide wire through a portionof the femur to extend out of a femoral head of the femur; securing areamer blade to the guide wire; reaming a femoral head outer surface atthe end of the femoral head to at least one of access cancellous boneand remove damaged cartilage; reaming an acetabulum outer surface of theacetabulum socket of the pelvis to at least one of access cancellousbone and remove damaged cartilage; unsecuring the reamer blade from theguide wire; and inserting a hemiarthroplasty cup between the femoralhead outer surface and the acetabulum outer surface.

In at least some embodiments, the method of joint replacement relates toforming one or more arthroscopy portals adjacent a hip joint thatincludes a femur and a pelvis; inserting a guide wire through a portionof the femur to extend out of a femoral head of the femur, securing areamer blade to the guide wire; reaming a femoral head outer surface atthe end of the femoral head to at least one of access cancellous boneand remove damaged cartilage; reaming an acetabulum outer surface of theacetabulum socket of the pelvis to at least one of access cancellousbone and remove damaged cartilage; unsecuring the reamer blade from theguide wire; rotating a cannulated drill around the guide wire andthrough the femur, inserting a cannulated fastener in place of thecannulated drill; inserting a cup femoral head prosthesis adjacent tothe femoral head outer surface; securing the cup femoral head prosthesisto the femoral head outer surface using the cannulated fastener, andinserting a hemiarthroplasty cup between the femoral head outer surfaceand the acetabulum outer surface.

In at least some embodiments, the method of joint replacement relates toforming one or more arthroscopy portals adjacent a hip joint thatincludes a femur and a pelvis; inserting a guide wire through a portionof the femur to extend out of a femoral head of the femur; securing areamer blade to the guide wire; reaming a femoral head outer surface atthe end of the femoral head to at least one of access cancellous boneand remove damaged cartilage; reaming an acetabulum outer surface of theacetabulum socket of the pelvis to at least one of access cancellousbone and remove damaged cartilage; unsecuring the reamer blade from theguide wire; rotating a cannulated drill around the guide wire andthrough the femur, inserting a cannulated fastener in place of thecannulated drill; inserting a cup femoral head prosthesis adjacent tothe femoral head outer surface; and securing the cup femoral headprosthesis to the femoral head outer surface using the cannulatedfastener.

In at least some embodiments, a device for joint replacement relates toa prosthesis including a hemiarthroplasty cup including an inner surfaceand an outer surface, wherein the inner surface is shaped and sized toaccommodate a reamed or unreamed femoral head outer surface, and whereinthe outer surface is shaped and sized to accommodate a reamed orunreamed acetabulum outer surface of an acetabulum socket.

In at least some embodiments, a device for joint replacement relates toa prosthesis including an at least partially hemispherical-shaped cupincluding an inner surface and an outer surface, wherein the innersurface is shaped and sized to accommodate a reamed femoral head outersurface of a femur, and wherein the outer surface is shaped and sized toaccommodate at least one of a reamed or unreamed acetabulum outersurface of an cetabulum socket and an inner surface of ahemiarthroplasty cup; a fastener securable to the femur for engagementwith a portion of the hemispherical-shaped cup to provide securement ofthe hemispherical-shaped cup to the femoral head outer surface.

In at least some embodiments, a device for joint replacement relates toa prosthesis including a hemiarthroplasty cup including an inner surfaceshaped and sized to accommodate a reamed or unreamed femoral head outersurface, and an outer surface shaped and sized to accommodate a reamedor unreamed acetabulum outer surface of an acetabulum socket, whereinthe hemiarthroplasty cup is configured to maintain allowance ofarticulation of the femoral head outer surface and the acetabulum socketrelative to the hemiarthroplasty cup after implantation.

In at least some embodiments, a device for joint replacement relates toa prosthesis including an at least partially hemispherical-shaped cupincluding an inner surface and an outer surface, wherein the innersurface is shaped and sized to accommodate at least one of a reamedfemoral head outer surface of a femur and a cup femoral head prosthesis,and wherein the outer surface is shaped and sized to accommodate areamed acetabulum outer surface of an acetabulum socket.

In at least some embodiments, a device for joint replacement relates toa prosthesis including a cup-shaped portion including an inner surfaceand an outer surface, wherein the inner surface is shaped and sized toaccommodate at least one of a reamed femoral head outer surface of afemur and a cup femoral head prosthesis, and wherein the outer surfaceis shaped and sized to accommodate a reamed or unreamed acetabulum outersurface of an acetabulum socket.

Other embodiments, aspects, features, objectives, and advantages will beunderstood and appreciated upon a full reading of the detaileddescription and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the method and device for joint replacement are disclosedwith reference to the accompanying drawings and are for illustrativepurposes only. The method and device for joint replacement is notlimited in its application to the details of construction or thearrangement of the components illustrated in the drawings. The methodand device for joint replacement is capable of other embodiments or ofbeing practiced or carried out in other various ways. In the drawings:

FIG. 1 illustrates a front view of a portion of an example of a humanbody with an example of a hip joint;

FIG. 2 illustrates an example of a front skeletal view of the hip jointof FIG. 1 ;

FIG. 3 illustrates a view of FIG. 2 with the femur distracted from thepelvis;

FIG. 4 illustrates another view of the femur and pelvis of FIG. 3 ;

FIG. 5 illustrates an example of a drill guide;

FIG. 6 illustrates an example of a guide wire and an example of areamer;

FIG. 7 illustrates a top view of the reamer of FIG. 6 ;

FIG. 8 illustrates the femur and pelvis of FIG. 3 and an example of ahemiarthroplasty cup prosthesis;

FIG. 9 illustrates a bottom view of the hemiarthroplasty cup prosthesis;

FIG. 10 illustrates a cross-sectional side view of the hemiarthroplastycup prosthesis taken at line 10-10;

FIG. 11A illustrates the femur of FIG. 3 with the guide wire positionedtherein;

FIG. 11B illustrates the femur of FIG. 3 with an example of a cannulateddrill positioned therein;

FIG. 11C illustrates the femur of FIG. 3 with an example of a cupfemoral head prosthesis and an example of a cannulated fastenerpositioned therein;

FIG. 11D illustrates the femur of FIG. 3 with the cup femoral headprosthesis secured to the femur;

FIG. 11E illustrates the femur of FIG. 3 with a view of the cup femoralhead prosthesis and cannulated fastener both inside and outside the hipjoint; and

FIG. 12 illustrates a view of the hip joint of FIG. 2 ,post-installation of the cup femoral head prosthesis and thehemiarthroplasty cup prosthesis.

DETAILED DESCRIPTION

Referring to FIG. 1 , a front view of a portion of an example of a humanbody 102 is illustrated. The body 102 is shown with a plurality of hiparthroscopy portals 105 identified. These hip arthroscopy portals 105are provided to allow access past skin 103, muscle, ligaments, etc., tothe hip joint 104 and are established as needed during a hiprepair/replacement procedure. The arthroscopy portals illustratedinclude an anterolateral portal 106, a midanterior portal 108, and adistal anterolateral portal 110, although one or more of various othertypes of arthroscopy portals can be provided in place of or in additionto these portals.

Referring to FIG. 2 , a front skeletal view of the hip joint 104 isprovided. The hip joint 104 includes at least portions of a pelvis 120and a femur 122. The femur 122 includes a femoral head 124 connected tothe femur 122 by a femoral neck 126. The pelvis 120 includes anacetabulum socket 128, which is a socket formed in the pelvis 120. InFIG. 2 , the femoral head 124 is shown in its natural seated position inthe acetabulum socket 128. FIG. 3 illustrates a view of the hip joint104 of FIG. 2 with the femur 122 distracted from the pelvis 120. Thedistraction exposes an acetabulum outer surface 130 and a femoral headouter surface 132. The acetabulum outer surface 130 and femoral headouter surface 132 are at least partially comprised of a layer ofarticular cartilage 141 (FIG. 4 ).

As a result of trauma, disease, and/or degeneration, the articularcartilage 141 can become damaged resulting in a rough or irregularsurface. In some cases, at least portions of the articular cartilage 141can be substantially worn away. These conditions reduce or eliminate thenormally smooth engagement of the femoral head 124 and the acetabulumsocket 128. In order to provide the smooth surfaces desired for properjoint function, one or both of the acetabulum outer surface 130 andfemoral head outer surface 132 are at least one of, resurfaced forengaging with a prosthesis or at least partially covered with aprosthesis. This can be achieved through at least the use of theprocedures and prosthesis as described below.

Referring now to FIG. 4 , another view of the hip joint 104 of FIG. 3 isillustrated. It is not evident by the illustrations, but it is to beunderstood that one or both of the acetabulum socket 128 and femoralhead 124 can be damaged or otherwise in need of repair or replacement.The procedure described below can include the use of one or more ofvarious tools as described below. FIG. 5 illustrates a drill guide 140utilized for inserting a guide wire 142 (FIG. 4 ) into the femur 122.The drill guide 140 includes an aiming arm 144 and a drill sleeve 146,both interconnected by a handle 148. In addition, referring to FIGS. 6and 7 , a reamer 150 is provided for resurfacing an end 151 of thefemoral head outer surface 132 and/or acetabulum outer surface 130. Thereamer 150 is shown as sickle-shaped, although it is contemplated thatthe shape and size of the reamer 150 can be modified as needed toaccommodate various bone and prosthesis shapes and sizes. A fasteningportion, such as a locking aperture 152 can be provided at a baseportion 154 of the reamer 150. The locking aperture 152 is configured tobe securable to the guide wire 142. The securement can be accomplishedby one or more of various methods, such as providing reverse threads 155in the locking aperture 152 for rotational engagement with reversethreads 155 on a guide wire end portion 158. In addition, the reamer 150includes an engagement portion 162 having a top edge 164 and bottom edge166. The top edge 164 includes a radius of curvature 167 shaped toconform to a desired shape for the acetabulum outer surface 130. Thebottom edge 166 includes a radius of curvature 167 shaped to conform toa desired shape for the end 151 of the femoral head outer surface 132.Further, the engagement portion 162 can be tapered as it extends awayfrom the base portion 154. In at least some embodiments, the top edge164 and bottom edge 166 each comprise a bladed edge, although othershapes and configurations can be utilized to provide the desiredresurfacing effect.

In at least some embodiments, to begin a hip joint repair or replacementprocedure, a patient is positioned on a hip arthroscopy traction table,in a supine, lateral, or other position as desired. The hip isdistracted, as illustrated in FIG. 4 , to provide the necessary accessto the femur 122 and acetabulum socket 128. The hip arthroscopy portals105 are formed as necessary, as shown in FIG. 1 . Upon entry into thebody 102, the hip ligamentous capsule (not shown) is cut to provide thenecessary access, for example from a 10 o'clock to 2 o'clock position.The drill guide 140 is then placed through the distal anterolateralportal 110 or others as desired, and the drill sleeve 146 is pushed tothe skin 103. After a small incision is made, the guide wire 142 isadvanced through the femur 122 by a drill (not shown) to its aimedlocation (determined by the positioning of the aiming arm 144 and drillsleeve 146), which is the center 170 of the femoral head 124. Afterinstallation of the guide wire 142, the drill guide 140 is removed andthe midanterior portal 108 is enlarged to provide greater access, suchas to a diameter of about 4 centimeters, or other necessary size. Theguide wire 142 is now positioned to receive the reamer 150. The reamer150 is inserted through the midanterior portal 108 and positioned so thereverse threads 155 of the guide wire 142 rotationally engage thereverse threads 155 of the locking aperture 152 to allow the reamer 150to be locked to the guide wire 142.

The drill is secured to the guide wire 142 and energized to rotate theguide wire 142. As the guide wire 142 rotates, the secured reamer 150also rotates. Placing a pulling tension on the guide wire 142, such thatthe bottom edge 166 of the rotating reamer 150 engages the end 151 ofthe femoral head outer surface 132, serves to ream down the end 151 ofthe femoral head outer surface 132 at least partially to cancellous boneand/or to remove damaged cartilage, thereby partially, substantially, orcompletely removing the articular cartilage layer from the femoral head124. The radius of curvature 167 along the bottom edge 166 of theengagement portion 162 can be chosen to form the end 151 of the femoralhead outer surface 132 to a desired shape, such as a symmetricalhemispherical shape. Similarly, advancing (pushing tension) the guidewire 142 during rotation, such that the top edge 164 of the rotatingreamer 150 engages the acetabulum outer surface 130, serves to ream downthe acetabulum outer surface 130 at least partially to cancellous boneand/or to remove damaged cartilage, thereby partially, substantially, orcompletely removing the articular cartilage layer from the acetabulumsocket 128. The radius of curvature 167 along the top edge 164 of theengagement portion 162 can be chosen to form the acetabulum outersurface 130 to a desired shape, such as a symmetrical hemisphericalshape. Upon completion of the reaming process, the reamer 150 is thensecured and the guide wire 142 is reversed in direction to disarticulatethe guide wire 142 from the reamer 150. The reamer 150 is then removedfrom the body 102. Therefore, use of the reamer 150 as described, canserve to prepare the femoral head 124 and the acetabulum socket 128 forreceiving or otherwise engaging each other or a prosthesis.

After completing the above procedure, various options exist forrepairing or replacing the hip joint 104. Referring to FIG. 8 , in atleast one embodiment, where a hemiarthroplasty (half joint replacement)is desired, the guide wire 142 can be removed and a hemiarthroplasty cup172 is inserted through the midanterior portal 108. The hemiarthroplastycup 172, as seen in FIGS. 8, 9, and 10 , is in at least someembodiments, a dual-sided hemispherical cup having a cup outer surface174 and a cup inner surface 176. The hemiarthroplasty cup 172 can in atleast some embodiments, be hemispherical, partially hemispherical, orsubstantially hemispherical, or otherwise sized to accommodate a reamedor unreamed joint bone. In addition, the hemiarthroplasty cup 172 caninclude alternate shapes, for example, an oblong/oval hemisphere. Thecup outer surface 174 is shaped and sized to pivotably engage theacetabulum outer surface 130 and can be installed without the use of anassisting fixation method, such as cement, fasteners, bone growthagents, etc. Similarly, the cup inner surface 176 is shaped and sized topivotably engage and articulate with the femoral head outer surface 132(or another prosthesis installed thereon) and can be installed withoutthe use of an assisting fixation method, such as cement, fasteners, bonegrowth agents, etc.

As the cup outer surface 174 can be installed without fixation, thefemoral head 124 and the acetabulum socket 128 are allowed to articulatewith the respective inner and outer cup surfaces 174, 176 of thehemiarthroplasty cup 172. The need for assistive fixation methods aresubstantially reduced or eliminated due to, at least in part due to, theminimal violation of the hip joint area during installation. Forexample, the above procedure does not require cutting the entireligamentous hip capsule (not shown) or significant cutting of themusculature of the hip, in order to prepare the hip joint 104 andinstall the hemiarthroplasty cup 172. The limited violation can maintainsufficient structure to support and secure the hemiarthroplasty cup 172as needed. In at least some embodiments, the hemiarthroplasty cup 172can be secured using assistive fixation methods, such as repair orreconstruction of the ligamentous capsule, or repair or reconstructionof the acetabular labrum, or another method as desired or necessary forone or more reasons.

As discussed above, various options exist for repairing or replacing thehip joint 104 after preparation of the hip joint 104. Referring now toFIGS. 11A-11E, in at least some embodiments, a cup femoral headprosthesis 180 can be installed on the femoral head 124. This procedureincludes securing the cup femoral head prosthesis 180 to the femoralhead 124. As seen in FIG. 11A, the guide wire 142 is positioned throughthe femur 122. In at least some embodiments, to fasten the cup femoralhead prosthesis 180, a cannulated drill 181 is rotated over the guidewire 142, as seen in FIG. 11B, until it passes out of the femoral headouter surface 132 at the center 170 of the femoral head 124. The guidewire 142 is secured and the cup femoral head prosthesis 180 is broughtinto the hip joint 104 through the midanterior portal 108. The guidewire 142 is then articulated with the cup femoral head prosthesis 180,while a cannulated fastener, such as a cannulated screw 184 with ananchoring head 185, is inserted into the femur 122 over the guide wire142, as seen in FIG. 11C. Further, as seen in FIG. 11C, the cup femoralhead prosthesis 180 is illustrated. The cup femoral head prosthesis 180can include numerous shapes, for example a shape similar to thehemiarthroplasty cup 172, such as a hemispherical, partiallyhemispherical, or substantially hemispherical cup shape. The cup femoralhead prosthesis 180 includes a femoral cup outer surface 186 and afemoral cup inner surface 188.

The cup femoral head prosthesis 180 can be utilized with or without thehemiarthroplasty cup 172. As such, if a hemiarthroplasty cup 172 is notto be installed, the femoral cup outer surface 186 is shaped and sizedto pivotably engage the acetabulum outer surface 130 (as seen in FIG. 8) after it has been reamed. If the hemiarthroplasty cup 172 is to beinstalled, the femoral cup outer surface 186 is shaped and sized topivotably engage the cup inner surface 176 of the hemiarthroplasty cup172. The femoral cup inner surface 188 is shaped and sized to fit theend 151 of the femoral head outer surface 132, after it has been reamed.The cup femoral head prosthesis 180 further includes a fastenerreceiving aperture 190 (see FIG. 11E) for engaging the cannulated screw184. In at least some embodiments, the receiving aperture 190 extendsthere through and includes threads 194 for engaging a threaded endportion 196 of the cannulated screw 184.

Referring to FIG. 11D, the cup femoral head prosthesis 180 is positionedover the femoral head outer surface 132 and the cannulated screw 184 issecured to the cup femoral head prosthesis 180. In at least someembodiments, this is accomplished by rotating the cannulated screw 184to engage the threaded end portion 196 with the receiving aperture 190and tightening of the cannulated screw 184 until the anchoring head 185is secured against a lateral femoral cortex 191 of the femur 122, andthe cup femoral head prosthesis 180 is secured onto the femur head outersurface 132. Once installed, the cup femoral head prosthesis 180provides a smooth and secure pivoting surface. After the fastening hasbegun or has been completed, the guide wire 142 can be removed, as seenin FIG. 11E. In at least some embodiments, the installation of the cupfemoral head prosthesis 180 is followed by the insertion of thehemiarthroplasty cup 172 into the hip joint 104, where thehemiarthroplasty cup 172 can be brought into the hip joint 104 throughthe midanterior portal 108. Upon completion of the installation of theprosthesis, the traction is taken off the hip joint 104 and the femoralhead prosthesis 180 is brought to articulate with the hemiarthroplastycup 172, as seen in FIG. 12 .

The cup femoral head prosthesis 180 and the hemiarthroplasty cup 172 canbe utilized together, or in isolation as a hemiarthroplasty. Inaddition, the cup femoral head prosthesis 180 and the hemiarthroplastycup 172 can be utilized together, or in isolation, without performing areaming procedure on a joint. The cup femoral head prosthesis 180 iscomprised of materials suitable for insertion into the body 102, such ascobalt chrome, steel, aluminum, and/or other alloys, metals, ceramics,polymer composites, etc. The inner surface 188 of the cup femoral headprosthesis 180 can be comprised of a porous, grit blasted, or otherwiseoriented surface amenable to either ongrowth or ingrowth of the bonefrom the femoral head outer surface 132. In addition, thehemiarthroplasty cup 172 is comprised of materials suitable forinsertion into the body 102, such as polyethylene, cobalt chrome, steel,aluminum, and/or other alloys, metals, ceramics, or polymer composites.The aforementioned material lists are not exclusive and therefore, othermaterials not listed or currently unknown can be used if suitable forsuch a purpose. Although the aforementioned procedure is described inrelation to hip joint 104, the components and procedures can be modifiedto accommodate repair and/or replacement of various other joints in thehuman body, such as a shoulder joint. For example, the shape of thereamer 150 could be modified to ream other ball and socket joints.Further, the components and procedures can be modified to accommodaterepair and/or replacement of a hip joint or other joints in the body ofan animal as well.

It is specifically intended that the method and device for jointreplacement not be limited to the embodiments and illustrationscontained herein, but include modified forms of those embodimentsincluding portions of the embodiments and combinations of elements ofdifferent embodiments as come within the scope of the following claims.Further, the steps outlined above can be modified in various manners,such as performance in one or more alternate orders. The addition orexclusion of any step(s) discussed or not discussed, does not preclude adesired completion of the procedure.

I claim:
 1. A prosthesis comprising: a hemiarthroplasty cup including:an inner surface shaped and sized to accommodate a reamed or unreamedfemoral head outer surface of a femoral head, wherein the inner surfacecomprises a hemisphere and is porous, an outer surface shaped and sizedto accommodate a reamed or unreamed acetabulum outer surface of anacetabulum socket, wherein the outer surface comprises a hemisphere andis smooth, an edge wall connecting the inner surface and the outersurface, the edge wall extending contiguously to form a planar andcircular surface, wherein the hemiarthroplasty cup is configured tomaintain allowance of articulation of the femoral head outer surface andthe acetabulum socket relative to the hemiarthroplasty cup afterimplantation; a cup femoral head prosthesis comprising; a hemisphericalinner surface configured to mate with a reamed femoral head outersurface; and a hemispherical outer surface configured to mate with andfreely articulate against the inner surface of the hemiarthroplasty cup;and a receiving aperture extending between the inner surface and theouter surface, the receiving aperture configured to receive an endportion of a fastener; and a fastener couplable to the cup femoral headprosthesis at the receiving aperture to provide securement of the cupfemoral head prosthesis to the femoral head outer surface, wherein thefastener comprises an end portion configured to be inserted into thereceiving aperture without extending beyond the hemispherical outersurface.
 2. The prosthesis of claim 1, wherein the hemiarthroplasty cupis configured to be installable through an arthroscopy portal withoutcutting completely through an entire perimeter of a ligamentous hipcapsule or musculature of a hip joint of the femoral head and theacetabulum socket.
 3. The prosthesis of claim 2, wherein thehemiarthroplasty cup is comprised of polyethylene or a polymer compositematerial.
 4. The prosthesis of claim 3, wherein the hemiarthroplasty cupis flexible.
 5. The prosthesis of claim 1, wherein the outer surface andthe inner surface of the hemiarthroplasty cup comprise hemispheres suchthat a thickness between the inner surface and the outer surface isuniform and the hemiarthroplasty cup does not encompass more than ahemisphere shape.
 6. The prosthesis of claim 1, wherein the fastener isa cannulated screw.
 7. The prosthesis of claim 6, wherein the cannulatedscrew comprises an anchoring head and a threaded end portion oppositethe anchoring head, the threaded end portion configured to be coupled tothe receiving aperture without extending beyond the hemispherical outersurface.
 8. The prosthesis of claim 1, wherein the hemispherical innersurface is shaped to mate with a reamed bone surface formed by asickle-shaped reamer having a bottom edge having a radius of curvaturematching that of the hemispherical inner surface.
 9. A prosthesis systemcomprising: a femoral head prosthesis comprising: an exteriorarticulating surface; an interior bone-engaging surface; and a receivingaperture extending from the exterior articulating surface to theinterior bone-engaging surface at a central portion of the femoral headprosthesis; a hemiarthroplasty cup comprised of solid materialincluding: an inner surface shaped and sized to freely articulateagainst an outer surface of the femoral head prosthesis; and an outersurface shaped and sized to accommodate a reamed or unreamed acetabulumouter surface of an acetabulum socket, wherein the hemiarthroplasty cupis configured to maintain allowance of articulation of the femoral headprosthesis outer surface and the acetabulum socket relative to thehemiarthroplasty cup after implantation; and a cannulated screwcomprising: a threaded end portion securable to the femoral headprosthesis at the receiving aperture such that the threaded end portiondoes not extend through the receiving aperture; and an anchoring headdisposed at an end of the cannulated screw opposite the threaded endportion.
 10. The prosthesis system of claim 9, wherein thehemiarthroplasty cup comprises a hemisphere-shaped body and the interiorbone-engaging surface is fabricated from porous material and theexterior articulating surface is smooth.
 11. The prosthesis system ofclaim 10, wherein a hemispherical inner surface of the femoral headprosthesis is shaped to mate with a reamed bone surface formed by asickle-shaped reamer having a bottom edge having a radius of curvaturematching that of the hemispherical inner surface.